Device and method for providing wavelength reduction with a photomask
Disclosed is a photomask having a wavelength-reducing material that may be used during photolithographic processing. In one example, the photomask includes a transparent substrate, an absorption layer having at least one opening, and a layer of wavelength-reducing material (WRM) placed into the opening. The thickness of the WRM may range from approximately a thickness of the absorption layer to approximately ten times the wavelength of light used during the photolithographic processing. In another example, the photomask includes at least one antireflection coating (ARC) layer.
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This application claims benefit and priority from U.S. Provisional Patent Application Ser. No. 60/511,503, filed on Oct. 15, 2003 and entitled “Device and Method for Providing Wavelength Reduction with a Photomask”.
The semiconductor integrated circuit (IC) industry has experienced rapid growth. Technological advances in IC materials and design have produced generations of ICs where each generation has smaller and more complex circuits than the previous generation. However, these advances have increased the complexity of processing and manufacturing ICs and, for these advances to be realized, similar developments in IC processing and manufacturing have been needed.
For example, in the course of integrated circuit evolution, functional density (i.e., the number of interconnected devices per chip area) has generally increased while feature size (i.e., the smallest component or line that can be created using a fabrication process) has decreased. This scaling down process generally provides benefits by increasing production efficiency and lowering associated costs, but needs to be matched by improvements in the fabrication process. For instance, many fabrication processes utilize a photomask to form a pattern during photolithography. The pattern may contain a pattern of designed circuits that will be transferred onto a semiconductor wafer. However, because of the increasingly small patterns that are to be used during photolithography, photomasks have generally needed increasingly high resolutions.
SUMMARYIn one embodiment, the present disclosure provides a photomask for forming a pattern during photolithography when illuminated with a predetermined wavelength of light. The photomask comprises a transparent substrate; an absorption layer proximate to the substrate, wherein the absorption layer has at least one opening formed therein; and a layer of wavelength-reducing material disposed in at least one opening, wherein a thickness of the wavelength-reducing material and the absorption layer form a generally planar surface.
BRIEF DESCRIPTION OF THE DRAWINGS
The present disclosure relates generally to photolithography and, more particularly, to using a wave-length reducing medium with a photomask. It is understood, however, that the following disclosure provides many different embodiments, or examples, for implementing different features of the invention. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.
Referring to
The absorption layer 104 may be formed using a number of different processes and materials, such as depositing of a metal film made with Chromium (Cr) oxide and iron oxide, or an inorganic film made with MoSi, ZrSiO, and SiN. The absorption layer 104 may be patterned to have one or more openings 108 through which light may travel without being absorbed by the absorption layer. In some embodiments, the absorption layer 104 may have a multi-layer structure, which may further include an antireflection (ARC) layer and/or other layers. In addition, some of these layers may be formed multiple times to achieve a desired composition of the absorption layer 104.
The absorption layer 104 may be tuned to achieve a predetermined transmittance and an amount of phase shifting, enabling the absorption layer 104 to shift the phase of light passing through the absorption layer, for improved imaging resolution. For example, the transmittance of the absorption layer 104 may be tuned to between approximately three percent and thirty percent, while the phase shift is tuned to approximately 180 degrees. This type of photomask is sometimes referred to as an attenuated phase-shifting photomask. In another example, the transmittance of the absorption layer 104 may be extremely high (e.g., 95%), and the phase shift may be approximately 180 degrees. This type of photomask is sometimes referred to as a chromeless phase-shifting photomask.
The WRM 106 may be used to fill in the one or more openings 108 of the absorption layer 104. The surface of the WRM 106 may be substantially co-planar with the surface of the absorption layer 104, but may be fine tuned to be slightly higher or lower with the plane of the surface of the absorption layer 104. Both materials may be planarized using known planarization techniques, such as chemical-mechanical planarization (CMP) to form a planar surface. The thickness of the WRM 106 may vary from less than to about the thickness of the absorption layer 104 (e.g., if the surface of the WRM is aligned with the surface of the absorber), to up to about ten times the wavelength of light passing through the WRM 106 during photolithographic processing. The WRM material used for the WRM 106 may be chosen based on a desired level of transparency and a desired refractive index. The WRM 106 preferably has a refractive index different from that of the absorption layer. In the present example, the WRM material is selected to provide both a high level of transparency and a high refractive index. Exemplary WRM materials include photoresist materials, polymer materials, and dielectric materials. For example, the material may include polyimide, SiO2, indium tin oxide (ITO), polyvinyl alcohol (PVA), or silicone.
During a photolithography process, the photomask 100 is disposed above a semiconductor formation. Typically, the photomask 100 does not come into contact with the surface of the semiconductor formation. Due to the relatively high refractive index (“n”) of the WRM 106, the wavelength of the light passing through the WRM 106 during photolithography processing may be reduced by a factor of n from the wavelength of the light in a vacuum. Since the physical size of the opening 108 in the absorption layer 104 remains the same, but the size of the opening 108 relative to the wavelength of the light is enlarged by the factor of n, optical diffraction is reduced accordingly and the resolution of imaging of the photomask 100 on a wafer may be enhanced.
Referring now to
In step 154 (
In step 156 and with additional reference to
Referring now to
For purposes of illustration, the ARC layers may include an ARC layer 210 on an underside (relative to the absorption layer 204) of the substrate 202, an ARC layer 212 between the substrate 202 and the absorption layer 204, an ARC layer 214 between the absorption layer 204 and the WRM 206, and/or an ARC layer 216 above the WRM 206. It is understood that the ARC layer 214 may not cover the sidewall of the patterned absorption layer 204, depending on a particular processing sequence or processing method used to form the photomask 100.
The ARC layers 210, 212, 214, 216 may be used at an interface to reduce stray light introduced by the photomask. Such interfaces may include an interface between the substrate 202 and the absorption layer 204 (using the ARC layer 212), an interface between the absorption layer 204 and the WRM 206 (using the ARC layer 214), and an interface between the substrate 202 and the WRM 206 (using the ARC layer 212), even though these ARC layers may function differently. For example, the ARC layer 214 on the absorption layer 204 may eliminate stray light contributed by the high reflectivity of the absorption layer. The ARC layer 216 on the WRM 206 may reduce multiple reflections between the outer face of the WRM 206 and the absorption layer 204. It may also reduce the reflection between the WRM 206 and the space outside. The ARC layer 212 on the substrate may reduce flare back into an illumination system used during photolithography and may provide a smooth transition between the substrate 202 and the WRM 206 to eliminate mismatch of the refractive index.
Each ARC layer may have multi-level structure that provides each ARC layer with multiple layers having different refractive indices. For example, the ARC layers may have a graded structure where the refractive index of each ARC layer changes gradually to match the refractive indexes of neighboring materials in the photomask 100. The ARC layers may comprise an organic material containing hydrogen, carbon, or oxygen; compound materials such as Cr2O3, ITO, SiO2, SiN, TaO5, Al2O3, TiN, and ZrO; metal materials such as Al, Ag, Au, and In; or combination thereof.
Referring now to
As previously described, materials used for the absorption layer 204 may include metal film such as Chromium (Cr) oxide and iron oxide, or inorganic films such as MoSi, ZrSiO, and SiN. The absorption layer 204 may be formed using CVD, plating, or PVD processes. In the present example, sputtering deposition may be preferred to provide the absorption layer 204 with thickness uniformity, relatively few defects, and better adhesion.
The ARC layers may use an organic material containing hydrogen, carbon, or oxygen; compound materials including Cr2O3, ITO, SiO2, SiN, TaO5, Al2O3, TiN, and ZrO; metal materials such as Al, Ag, Au, and In; or combination thereof. Methods used to form the ARC layers include spin-on coating, CVD, plating, or PVD.
In step 254, the absorption layer 204 and the ARC layer 214 may be patterned to have a predefined arrangement of openings as previously described with respect to the method 150 of
Referring now to
For purposes of illustration, the ARC layers may include an ARC layer 310 on an underside (relative to the absorption layer 304) of the substrate 302, an ARC layer 312 between the substrate 302 and the absorption layer 304, an ARC layer 314 between the absorption layer 304 and the WRM 306, and/or an ARC layer 316 above the WRM 306. These ARC layers are similar to those described with respect to
Referring now to
In step 354, the absorption layer 304 may be patterned to have a predefined arrangement of openings as previously described and, in step 356, the ARC layer 314 is formed. Since the ARC layer 314 is formed after the absorption layer 304 is formed and patterned, the ARC layer 314 conforms to the shape of the absorption layer 304. This enables the ARC layer 314 to be formed over the sidewalls of the absorption layer 304 (
The present disclosure has been described relative to a preferred embodiment. Improvements or modifications that become apparent to persons of ordinary skill in the art only after reading this disclosure are deemed within the spirit and scope of the application. It is understood that several modifications, changes and substitutions are intended in the foregoing disclosure and in some instances some features of the invention will be employed without a corresponding use of other features. For example, one or more of the illustrated ARC layers may be excluded or additional ARC layers may be used. Materials used for the transparent substrate, absorption layer, wavelength reducing material, and ARC layers may vary, as may the method by which the various layers are formed. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the scope of the invention.
Claims
1. A photomask for forming a pattern during photolithography when illuminated with a predetermined wavelength of light, the photomask comprising:
- a transparent substrate;
- an absorption layer proximate to the substrate, wherein the absorption layer has at least one opening formed therein; and
- a layer of wavelength-reducing material disposed in the at least one opening, wherein the wavelength-reducing material and the absorption layer form a generally planar surface.
2. The photomask of claim 1 wherein a thickness of the wavelength-reducing material is substantially equal to a thickness of the absorption layer.
3. The photomask of claim 1 wherein the wavelength-reducing material forms a generally planar surface beyond the absorption layer.
4. The photomask of claim 1 wherein the wavelength-reducing material thickness is less than or equal to about ten times the predetermined wavelength of the light.
5. The photomask of claim 1 wherein the wavelength-reducing material has a refractive index larger than 1 and a transmissivity of more than 10%.
6. The photomask of claim 1 wherein the wavelength-reducing material comprises a transparent polymer material.
7. The photomask of claim 1 wherein the wavelength-reducing material comprises a photoresist material.
8. The photomask of claim 1 wherein the wavelength-reducing material comprises a transparent dielectric material.
9. The photomask of claim 1 wherein the absorption layer has a transmissivity of between 1% and 100% and is adapted to modify a phase of light passing through the absorption layer, and wherein the wavelength-reducing material has a refractive index larger than 1 and a transmissivity of more than 10%.
10. The photomask of claim 1 wherein wavelength-reducing material has a refractive index different from that of the absorption layer.
11. The photomask of claim 1 further comprising at least one antireflection coating layer.
12. The photomask of claim 1 further comprising at least one antireflection coating layer on the wavelength-reducing material.
13. The photomask of claim 1 further comprising at least one antireflection coating layer on the substrate.
14. The photomask of claim 1 further comprising at least one antireflection coating layer between the absorption layer and the wavelength-reducing material.
15. The photomask of claim 11 further comprising at least one antireflection coating layer between the wavelength-reducing material and the substrate.
16. The photomask of claim 1 further comprising at least one antireflection coating layer between the absorption layer and the substrate.
17. The photomask of claim 1 further comprising at least one antireflection coating layer with a graded structure.
18. A method for fabricating a photomask on a transparent substrate, the method compromising:
- forming an absorption layer proximate to the substrate;
- patterning the absorption layer and forming at least one opening in the absorption layer; and
- forming a wavelength-reducing material in the at least one opening of the absorption layer.
19. The method of claim 18 further comprising forming an antireflection coating layer on a side of the substrate opposite the wavelength-reducing material.
20. The method of claim 18 further comprising forming an antireflection coating layer on the wavelength-reducing material.
21. The method of claim 18 further comprising forming an antireflection coating layer between the substrate and the wavelength-reducing material.
22. The method of claim 18 further comprising forming an antireflection coating layer between the substrate and the absorption layer.
23. The method of claim 18 further comprising forming an antireflection coating layer between the wavelength-reducing material and the absorption layer.
24. The method of claim 18 wherein forming the wavelength-reducing material comprises a spin coating process.
25. The method of claim 18 wherein forming the wavelength-reducing material comprises a sputtering deposition process.
26. The method of claim 18 wherein forming the wavelength-reducing material comprises a chemical vapor deposition process.
27. The method of claim 18 wherein forming the wavelength-reducing material comprises an atomic layer deposition process.
28. The method of claim 18 wherein forming the wavelength-reducing material comprises a physical vapor deposition process.
29. The method of claim 18 wherein forming the wavelength-reducing material comprises limiting a thickness of the wavelength-reducing material between about a thickness of the absorption layer to approximately ten times a predefined wavelength of light.
30. The method of claim 18 wherein forming the wavelength-reducing material comprises a planarizing process.
31. A photomask comprising:
- a substantially transparent substrate;
- an absorption layer proximate to the substantially transparent substrate and defining at least one opening therein; and
- a high refractive index layer disposed in the at least one opening of the absorption layer and operable to reduce a wavelength of light passing therethrough during photolithography.
32. A photolithography method comprising:
- positioning a photomask above a semiconductor formation, the photomask comprising: a substantially transparent substrate; an absorption layer proximate to the substantially transparent substrate and defining at least one opening therein; and a high refractive index layer disposed in the at least one opening of the absorption layer and operable to reduce a wavelength of light passing therethrough during photolithography;
- exposing the semiconductor formation and photomask to light.
Type: Application
Filed: Oct 13, 2004
Publication Date: May 12, 2005
Applicant: Taiwan Semiconductor Manufacturing Company, Ltd. (Hsin-Chu)
Inventors: Burn Lin (Hsin-Chu), Jeng Chen (Hsin-Chu), Chun-Kuang Chen (Hsin-Chu), Tsai-Sheng Gau (Hsin-Chu), Ru-Gun Liu (Hsin-Chu), Jen-Chieh Shih (Hsin-Chu)
Application Number: 10/964,842